require 'rmagick'

imgl = Magick::ImageList.new
imgl.new_image(300, 100, Magick::HatchFill.new('white', 'lightcyan2'))

points = [
  12, 93.75, 37, 93.75, 37, 81.25, 62, 81.25,
  62, 93.75, 87, 93.75, 87, 62, 112, 62, 112, 93.75,
  137, 93.75, 137, 43.75, 162, 43.75, 162, 93.75,
  187, 93.75, 187, 25,    212, 25,    212, 93.75, 237, 93.75,
  237, 6.25,  262, 6.25,  262, 93.75, 287, 93.75
]

gc = Magick::Draw.new
gc.stroke('blue').stroke_width(3)
gc.fill_opacity(0)
gc.polyline(*points)

gc.draw(imgl)

imgl.border!(1, 1, 'lightcyan2')

imgl.write('polyline.gif')
